Compact Blade Pivot Design for Turbo Machine Fan Hubs
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Solution Overview
Problem
The existing architecture of turbojet fan hubs with high bypass ratios requires bulky dimensions to accommodate blade pitch change mechanisms and rolling bearings, limiting the integration of more blades and increasing mass, which hampers efficiency and reliability.
Innovation Solution
A compact blade pivot design with a ball bearing for centrifugal forces and a needle or roller bearing for transverse forces, featuring a timing transmission ring inside the stud, allowing for reduced hub diameter and increased blade count, while providing flexibility to absorb vibrations and simplify pitch change systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the inner and outer rolling bearings are radially very spaced to minimize transverse forces on the inner bearing, then the inner bearing can be wider and placed on a very low radius, but the tangential space between adjacent bearings is restricted and the fan hub diameter is increased
Solution Approach 1:
The bearing system is divided into two separate functions: the inner bearing handles centrifugal forces while the outer bearing handles transverse forces. This segmentation allows each bearing to be optimized for its specific function, with the outer bearing positioned to handle transverse forces without requiring excessive radial spacing, thereby reducing the overall hub diameter.
Solution Approach 2:
The outer rolling bearing acts as an intermediary element that absorbs transverse forces, preventing these forces from being transmitted to the inner bearing. This mediator approach allows the inner bearing to focus solely on centrifugal forces, enabling more compact radial positioning and reducing the hub diameter.
2Force
If the inner rolling bearing is placed on a very low radius to absorb centrifugal forces, then the bearing can be wider, but the tangential space between inner rolling bearings of adjacent blades is very restricted
Solution Approach 1:
By segmenting the bearing functions between inner and outer bearings, the inner bearing can be positioned at low radius for centrifugal force absorption while the outer bearing handles transverse forces. This division allows adequate tangential space between adjacent blade bearings since the outer bearing's transverse force absorption function eliminates the need for excessive radial spacing.
3Reliability
If the fan hub diameter is increased to accommodate the bearing arrangement, then the bearings can be properly positioned, but the number of blades that can be integrated per hub is reduced
Solution Approach 1:
The segmentation of bearing functions allows for a more compact hub design. The inner bearing handles centrifugal forces while the outer bearing handles transverse forces, enabling the hub to accommodate more blades within the same diameter constraints, thereby increasing productivity without compromising reliability.
4Force
If traditional pivot architecture with bulky bearings is used, then force absorption is ensured, but the mass of the hub and blades is increased
Solution Approach 1:
By segmenting the bearing system into inner and outer bearings with distinct functions, the design achieves efficient force absorption with reduced mass. The inner bearing's specialized centrifugal force absorption and the outer bearing's transverse force absorption function together to provide comprehensive force management while minimizing the overall mass of the hub and blade assembly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design reduces the fan hub diameter, enables more blades per hub, and enhances reliability by distributing centrifugal forces efficiently, reducing mass and machining complexity, while preventing vibration propagation during flight events.
Implementation Method 1
a ball bearing for absorbing centrifugal forces
Implementation Method 2
a centrifugal force-recovering ball bearing having an inner ring mounted in transverse abutment against an outer radial portion of the stud
Implementation Method 3
a needle or roller bearing which allows precise guidance and a gain in compactness
Data Source
Figure 1
Figure 2
Figure 3A~3F
AI summary
The invention relates to a blade pivot (2) of adjustable orientation for a turbomachine fan hub, comprising a block (4) having retaining means (10) configured to retain a fan blade root (12) and coupling means (16) for the transmission of a torque, a ball-type rolling bearing (26) for taking up centrifugal forces having an inner ring (28), a clamping nut (42) screwed onto an external thread (44) of the block in order to clamp the inner ring of the ball-type rolling bearing for taking up centrifugal forces onto the block, a rolling bearing (34) for taking up transverse forces, a wedging transmission ring (18) positioned inside the inner radial end of the block and provided with coupling means (20) cooperating with the coupling means (16) of the block, and means (22, 24) for locking the wedging transmission ring on the block.